1. Field of the Invention
The present invention relates to an image projecting system and an image projecting method that are favorably applied to projecting images onto a screen using a plurality of projector apparatuses, a computer program applied to a processing method thereof, and to a recording medium that stores such computer program.
2. Description of the Related Art
In the past, to realize a large-screen display that has high resolution, a method of projecting a large image by arranging a plurality of projector apparatuses in a grid has been proposed.
FIG. 1 shows an example construction of an existing image projecting system 100 constructed of a plurality of projector apparatuses. The image projecting system 100 includes N projector apparatuses, a screen 102 as a display screen for projected images, an observation unit 104 that observes the images projected onto the screen 102, and a control apparatus 105 that receives information observed by the observation unit 104 and supplies image signals to the projector apparatuses. However, in FIG. 1 only the projector apparatuses 101-1 to 101-4, 101-11 to 101-14, and 101-21 to 101-24 are shown. Each projector apparatus projects an image onto the screen 102 and by joining the images projected by the respective projector apparatuses, a single image is constructed as a whole. In this way, one large image is formed on the entire screen 102. Note that in the following description, the image projected onto the screen 102 by one projector apparatus is referred to as a “projected image”. In FIG. 1, the projected image projected onto the screen 102 by the projector apparatus 101-12 is set as the “projected image 103-12”.
FIG. 2 is composed of three views of the image projecting system 100 that are a front view, a side view, and an upper view. The projected image 103-12 is highlighted for comparison with the projected images produced by the other projector apparatuses. In the past, when an image is projected onto the screen 102 using a plurality of projector apparatuses, parts (i.e., edge portions) of adjacent projected images overlap.
However, when an image is projected using the image projecting system 100, the “joins” of the adjacent projected images are conspicuous. For this reason, before an image is presented, preprocessing (calibration) is normally carried out to prevent the joins of adjacent projected images from being conspicuous.
The following two methods are known as representative types of preprocessing (calibration).
(1) Geometric Correction
It is difficult to accurately lay out the projector apparatuses so that a plurality of projected images projected by adjacent projector apparatuses join up. For this reason, geometric conversion is carried out in advance on the image to be presented so that the plurality of projected images join up. FIGS. 3A and 3B are diagrams showing projected images when the screen 102 is set as an xy plane. In FIGS. 3A and 3B, the projected image 103-11 of the projector apparatus 101-1 and the projected image 103-12 of the projector apparatus 101-2 are extracted from the plurality of projected images. Here, it is assumed that grid patterns are displayed in the projected images 103-11, 103-12. The projector apparatuses 101-1, 101-2 are slightly displaced in the horizontal direction due to the positions in which the apparatuses have been set up.
FIG. 3A shows an example display of the projected images before geometric correction.
Before geometric correction, the grids of the projected images 103-11, 103-12 are displayed in a displaced state. For this reason, the horizontal lines and vertical lines in the images become crooked, which is not favorable.
FIG. 3B shows an example display of the projected images after geometric correction.
After geometric correction, the grids of the projected images 103-11, 103-12 are displayed on top of one another. The horizontal lines and vertical lines in the images are displayed without being crooked.
In this way, by carrying out geometric correction on the images to be projected by the respective projector apparatuses, an image can be displayed on the entire screen 102 without displacements.
(2) Luminance/Color Correction
Even for projector apparatuses of the same model, due to fluctuations in the characteristics of the internal optical elements, the projector lamps, and the like, there can be differences between individual apparatuses in the intensity of the outputted light and the intensity balance of the RGB colors. Also, in regions where the projected images projected by adjacent projector apparatuses are superimposed, since the intensities of light from two projector apparatuses are added, such regions will become extremely bright compared to the periphery thereof.
FIG. 4 is a photograph showing one example of the fluctuations in luminance and color between the projected images projected using the image projecting system 100. In a state where the projector apparatuses are disposed in a tile pattern and the same input (white light, where (R,G,B)=(255,255,255)) is used for the respective projector apparatuses, a part of the image projected on the screen is picked up by the observation unit. Each rectangular region in FIG. 4 corresponds to one projector apparatus. Here, it can be seen that there are fluctuations in luminance and color between the adjacent projector apparatuses 103-12, 103-32. It can also be seen that there are differences in the luminance between projector apparatuses and differences in color even for the same white color. Also, it can be seen that there are fluctuations in luminance and color even within the projected image of the same projector apparatus.
For this reason, to even out the imbalances in luminance, luminance correction is carried out as shown in FIGS. 5A and 5B. FIGS. 5A and 5B are explanatory diagrams where the luminance L of the images projected onto the screen 102 from the projector apparatuses 101-11, 101-12 is shown on the vertical axis and the xy plane on the screen 102 is shown on the horizontal axis.
FIG. 5A shows examples of the luminance of projected images before luminance correction.
Before luminance correction, the luminances of the images projected from the projector apparatuses 101-11, 101-12 are shown by curved lines. Since the luminance increases at the position where adjacent projected images are superimposed, a bright line appears on the screen.
FIG. 5B shows examples of the luminance of projected images after luminance correction.
After luminance correction, the luminances of the images projected from the projector apparatuses 101-11, 101-12 are shown by straight lines. The projected images before luminance correction are shown by broken lines for comparison purposes. Since the increased luminance at a position where adjacent projected images are superimposed is substantially matched to a flattened luminance, a bright line does not appear on the screen.
Aside from the technologies described above, various other calibration technologies have been proposed.
Japanese Unexamined Patent Application publication No. 2006-109168 discloses a technology for displaying images projected from three projector apparatuses as one image on a screen.
Japanese Unexamined Patent Application Publication No. 2007-251294 discloses a technology that projects and superimposes a color correcting image to correct nonuniformity in a color distribution produced in images when a plurality of images are projected so as to be adjacent to one another.